Interstand tension-compression control system

ABSTRACT

An interstand tension control system is disclosed for use in a continuous mill having a plurality of stands, each stand having an electric motor for actuating rollers for successively rolling material to a predetermined cross sectional area. After impact of the material into the first stand, there is a delay, and then the rolling load is read and held in memory. After impact of the material at the succeeding stand, there is another time delay after which the load now in stand one is read and compared with that held in memory. If there is a difference, stress is being exerted on the material being rolled. Corrective measures are then taken to adjust the speed of the motor for the succeeding stand until the load at stand one is equal to that held in memory, so that substantially no tensile or compressive stress is now exerted on the material.

United States Paten Hensleigh a Apr. 30, 1974 INTERSTAND TENSION-COMPRESSION Primary Examiner-Milton S. Mehr CONTROL SYSTEM Attorney, Agent, or Firm-J. J. Wood 75 l t Ml nven or Nita/in A Henslergh, williamsville, ABSTRACT I h An interstand tension control system is disclosed for [73] Asslgnee: Westmghouse Elecmc Corporauon, use in a continuous mill having a plurality of stands,

Plttsburgh, each stand having an electric motor for actuating rol- [22] Filed: July 31, 1972 lers for successively rolling material to a predetermined cross sectional area. After impact of the mate- PP No.: 276,490 rial into the first stand, there is a delay, and then the rolling load is read and held in memory. After impact 52 us. on. 72/19 of the material at the sqcceeding Stand there is [51,] Int. Cl B2lb 37/00 Pther delay after whl ch the load w" stand one [58] Field of Search 72/8, 19, 28; 318/80 18 reafi compared Wlth that held In y- If there IS a difference, stress is being exerted on the ma- 5 References Cited terial being rolled. Corrective measures are then taken UNITED STATES PATENTS to ad ust the speed of the motor for the succeeding stand until the load at stand one is equal to that held g fz 3 2 in memory, so that substantially no tensile or compres- 3:688:532 9/1972 ...:2:I.........................::::H2/ 6 sive stress is nowrxefled the material 6 Claims, 3 Drawing Figures [O B so n*=5TAND#l E 20 r n*=srAND#2 FIELD SPEED REE |6\ E} FIELD SPEED REE EXcITERa EXCITER a k SPEED REG SPEED REGV -|4 STAND TO TRANSPORT DELAY MANUAL SPEED ADJUST l MASTER l 64 L MANUAL WFI' SPEED ADJUST i 1 mimcnmsmw 807,208

sum 2 BF 2' (n 1 TENSION l I ERROR v I I I I I' to t t2 t3 t4 STAND#| TIME FIG. 2

COMPRESSION Y ERROR a O. E

o l 2 s M STAND#I TIME INTERSTAND TENSION-COMPRESSION CONTROL SYSTEM BACKGROUND OF THE INVENTION sult of over or under filling a roll pass. The practice of rolling steel has established that pass friction is changed with tension thereby affecting a section change in the 7 roll bite.

In the past the operator in his pulpit carefully watched the mill stand ammeters, and adjusted the speed of the mill stand motors. Manual adjustment in many cases made the results fortuitous at best. The instant invention enables the operator to arrive at no stress rolling conditions in a disciplined manner, without the utilization of elaborate and expensive remote tension sensing devices;

SUMMARY OF THE INVENTION In accordance with the principles of the invention there is provided a system for controlling interstand tension and compression in a continuous rolling mill having a plurality of stands. Each stand has an electrical motor for actuating the rollers for successively rolling material to a predetermined crosssectional area. Means are provided for detecting the entrance of the material into the first stand rollers, and for developing a first load detecting signal. First delay means, actuated in response to the first load detecting signal, deliver a first delay signal after a predetermined time delay. Means actuated in response to the first delay signal, are provided for memorizing the armature current Ialm of the first stand motor. Seconddelay means are provided for detecting the presence of the material in the succeeding second stand rollers for delivery'of a second load detecting signal. Means, actuated in response to the second load detecting signal, are provided for comparing the instantaneous armature current Ial of the first motor with the armature current Ialm held in memory and for delivering a polarized compared signal. Then, means actuated in response to the polarized compared signal, increase ordecrease the speed of the second motor until the compared signal is zero, i.e.'

when [a1 Ialm.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF AN EXEMPLARY EMBODIMENT The interstand tension-compression control system of the invention is here illustrated in the environment of a bar or billet mill. 'Usually such a mill will include roughing, intermediate and finishing sections. For example, the roughing mill may comprise six stands, the intermediate mill four stands, and the finishing mill may have as many as six stands. For simplicity, in FIG. 1, only two stands 10, 12 are shown, although it will be obvious from the description that the system is readily expandable to include as many stands as desired.

The l0, l2 stands respectively comprises rollers indicated symbolically at 14, 16 coupled through gearing 18, 20 to electric motors (usually a DC. shunt motor) indicated at 22, 24. The stand motors 22, 24 are connected to a common bus 26.

The motor 22 has a shunt field 28 which is connected to a field exciter and speed regulator indicated symbolically by the box identified at 30. (The corresponding components for motor 24 are identified at 32 and 34). A tachometer generator 36 is coupled to the shaft of motor 22. Similarly, tachometer generator 38 is coupled to the shaft of motor 24. Shunt resistors at 40, 42 enable the armature currents of motors 22 and 24 to be monitored, the armature currents being applied to amplifiers 44, 46 respectively as shown.

A load detecting means for STAND ONE is indicated generally at 48. Similarly, a load detecting means for STAND TWO is indicated generally at-50.

The load detecting means 48 comprises: the tachometer generator previously identified at 36, a summation amplifier 52, a capacitor 54 and a relay lLD having normally open contacts lLDl.

The scheme for identifying the various relays is as follows: The prefix indicates the stand number with which the relay is associated. The letters will, wherever possible give an indication of the function to be performed by the relay i.e., LD is load detecting. The numeration following the letters indicates the identification of the contacts. A bar under the numeral indicates that the contacts are normally closed, while no bar indicates that they are normally open.

Accordingly, the various relays together with their relay contacts are identified as follows:

lLD first stand load detector relay lLDl first stand load No. 1 relay contacts 2 LD second stand load detector relay 2 LDl second stand load No. l relay contacts 2LD2= second stand load No. 2 relay contacts lCR first stand contact relay lCRl first stand contact No. '1 relay contacts 2CR second stand contact relay 2CR1 second stand contact No. l relay contacts lTD first stand transport delay relay lTDl first stand transport No. l relay contacts (normally closed) 2TD second stand transport delay relay 2TD1 second stand transport No. 1 relay contacts (normally closed) 2TD2 second stand transport No. 2 relay contacts (normally closed) 1STD first stand speed transport delay relay 1STD1 first stand speed No. 1 relay contacts 2STD second stand speed transport delay relay 2STD1 second stand speed No. l relay contacts 3TD1 third stand speed transportdelay No. 1 relay contacts The second stand load detecting means 50 comprises the tachometer generator previously identified at 38, a

summation amplifier'56, a capacitor 58 an a relay 2LD having contacts 2LD1, 2LD2.

The speed changing means for STAND ONE and STAND TWO are identified at 60 and 62 respectively. The speed changing means 60 comprises an amplifier 64 which drives a motor-potentiometer 66,68. A motor operated potentiometer of this kind is well known in the art e the motor drives the slider of the potentiometer so that the slider picks of a voltage, the potentiometer being connected between a source of potential (here the master speed reference) and ground. A manual speed adjustment input, provides a voltage signal input which determines the initial positioning of the respective slides of the potentiometers.

The speed adjusting means 62 is similar to the speed adjusting means 60, and comprises amplifier 70, and motor-potentiometer 72,74, the only difference being that amplifier 70 has an additional input which is applied through contacts 2LD2. In this respect all the succeeding STANDS THREE, FOUR ect. will be similar to STAND TWO.

A memory means for STAND ONE is identified generally at 76. (In the interests of simplicity, the memory means for STAND TWO is not shown.) The memory means 76 comprises an amplifier 78, the output of which is applied through contacts lCRl to an operational amplifier indicated generally at 80, connected as an integrator. The operational amplifier 80 comprises resistor 82, amplifier 84 and feedback capacitor 86. The output of the operational amplifier 80 is fed back to the input of amplifier 78 and to a summation amplifier 88 associated withSTAND TWO.

A transport delay means for STAND ONE is identified generally at 90, and comprises an operational amplifier 92 operated as an integrator, and a voltage comparator 94. The operational amplifier 92 includes an input resistor 96 applied to an amplifier 98 having a capacitor 100 in the feedback loop. v

The voltage comparator 94 includes an amplifier 102 which receives one input from the operational amplifier 92, the other input being connected to the slider of a potentiometer 104 which isconnected between a source of negative potential and ground as indicated.

OPERATION OF THE EXEMPLARY EMBODIMENT Initially, the operator in the pulpit, (the command console situs), presets each stand at its expected operating speed at no load conditions according to the effective' mill rolling constant. The mill motors may then be decelerated by reducing the bus voltage to percent of the rated voltage. The percentage is higher if the bar head and transport delays are of such magnitude so as to allow the tension system to function in approximately 1 /2 to 2 sec.

The operator then selects the Automatic Stand Speed Set (A pushbutton to initiate the interstand tension system) of the instant invention. A bar or billet from the heating furnace now enters STAND ONE. The current from themotor 22 passes through-the shunt 40 to the amplifier 44'. The output Ial (the armature current of themotor of STAND ONE) of amplifier 44 is applied: to the summing amplifier 52, to the amplifier 78 and to the summation amplifier 88.

The output of the tachometer generator 36 is connected to the input of amplifier 52 through capacitor 54. This output is also connected to the speed transport delay means 90.

delay means 90 through contacts 1STD1 of the speed transport delay relay lSTD.

The load detector detects when the billet is in STAND ONE: thus, during acceleration 'or deceleration, the change in voltage results in a voltage at the capacitive input of amplifier 52 which is equal and opposite to the voltage at the other input, and relay lLD remains inactivated. However, the load torque required to roll the billet results in an increase in the motor armature current Ial, the resulting unbalance producing output signal at the output of amplifier 52 which actuates the relay lLD.

As may be seen from the relay diagram, the closing of normally open contacts lLDl electrically completes the circuit for both relays 1CR and ISTD. The relay contacts lCRl and 1STD1 close simultaneously actuating the memory means 76 and the first transport The billet transport delay means 90 is intended to cease operation or to be deactivated when the billet is about to enter STAND TWO. The memory means 76 then retains a voltage which is a function of the current Ialm, which in turn is a function of the actual load torque required to roll the billet.

At the memory 76, the input lalm is applied to the amplifier 78; the output of the amplifier 78 is applied through now closed contacts lCRl to the integrator 80. The amplifier 84 acts as an inverter, and the output Ialm' is negative. By the feedback path, Ialm is applied to the input of amplifier 78. Because of the opposite polarity of the applied signals, the amplifier 78 will continue to produce an output, until the inputs are equal in magnitude, i.e., Ial =Ia 1m. When the contacts lCRl open again, the integrator by virtue of the charged camoving from STAND ONE to STAND TWO. When the positive potential equals the negative potential setting of the potentiometer 104, the relay ITD is actuated, causing normally closed contact lTDl to open;

' this inactivates relay lCR, opening contacts lCRL.

If STAND TWO is running too fast lal la1m, it is pulling on the billet creating a tension in the billet. STAND ONE is therefore doing less work, and Ial will be less than lalm. A negative voltage at the output of amplifier 88 will cause motor 72 to rotate so as to move the potentiometer 74 in such direction so as to decrease the speed of motor24. The slider of potentiometer 74 provides the speed reference-n* for the motor 24, the speed of which is controlled by field weakening.

The action of motor 24 will have an effect on what is happening at STAND ONE. Obviously, as motor 24 pulls less on the billet tension will decrease, and lal will increase until it equals lalm.

lal lalm .lf STAND TWO motor 24 isrunning too slow vis-avis the STAND ONE motor 22, then STAND ONE motor 22 is pushing on the billet and subjecting it to negative tension or compression. The load on STAND ONE is greater, and lal lalm. The output of amplifier 88 is therefore and the motor 72 drives the potentiometer 74 in such direction as to increase the speed of STAND TWO motor 24 until lal lalm.

The billet of course has been in continuous transit toward STAND THREE. Similarly, as the billet approaches STAND THREE the transport delay means for STAND TWO is actuated, opening the closed contacts 2TD 1 isolating STAND ONE and opening the normally closed contacts 2TD2. The process is now repeated as between STANDS TWO AND THREE.

The condition Ial lalm is further depicted in FIG. 2. The curve A represents the armature current without correction; curve B represents the armature current in the practice of the invention. After the billet has entered STAND ONE and the transients have subsided,

at t1 (impact recovery) there is represented the arma- 1 ture current required to roll the billet. At t2 the billet has entered STAND TWO, at :3 there is impact recovery, and at 14, the interstand tension compression system of the invention begins to look at the situation and begin correction.

The condition lal lalm is depicted in FIG. 3. Similarly the system at t4 begins to look at the error due to compression and make correction.

Once the motors have been set at the proper speeds, the mill operator can then turn off the automatic stand speed set and proceed to continuously roll billets.

I claim:

1. An interstandtension-compression control system for use in a continuous mill having a plurality of stands,

each stand having an electric motor for actuating rollers for successively rolling material to a predetermined cross sectional area comprising:

a. first detecting means for sensing the presence of said material in the first stand rollers and for developing a first load detecting signal;

12. memory means actuated in response to said first load detecting signal and connected to receive the armature current lal of the first stand motor, for

memorizing the armature current lalm;

c. first transport delay means actuated in response to said first load detecting signal, and arranged to receive a first voltage proportional to the speed of said first motor, and to deliver a first transport delay signal which is an inverse function of the first motor speed, said first transport delay signal inactivating said memory means, said latter means retaining the memorized armature current lalm; second detecting means for sensing the presence of said material in the succeeding second stand rollers, and for developing a second load detecting signal;

e. algebraic summation means actuated in response to said second load detecting signal and adapted to receive the polarized instantaneous armature current lal, of said first motor, and the polarized memorized armature current lalm, and to deliver an algebraic summation signal which becomes zero when Ial lalm;

speed changing means actuated upon receipt of said second load detecting signal for increasing or decreasing the speed of the second stand motor, said second motor speed changing means being connected to receive said algebraic summation signal, and to change the speed of said second stand motor as a function of said algebraic summation signal; and second transport delay means actuated in response to said second load detecting signal, arranged to receive a second voltage proportional tothe speed of said second motor and to deliver a second transport delay signal which is an inverse function of the second motor speed, said second transport delay signal electrically isolating the first stand from the second stand, the material having now traversed from the first stand to the second stand under substantially no tensile or compressive stress.

2. An interstand tension-compression control system for use in a continuous mill having a plurality of stands, each stand having an electric motor for actuating rollers for successively rolling material to a predetermined cross sectional area comprising, first detectingmeans for sensing the presence of said material in the first stand rollers and for developing a first load detecting signal, memory means actuated in response to said first load detecting signal .and connected to receive the armature current lal of the first stand motor, for memorizing the armature current lalm, first transport delay means actuated in responce to said first load detecting signal, and arranged to receive a first voltage proportional to the speed of said first motor, and to deliver a first transport delay signal which is an inverse function of thefirst motor speed, said first transport delay signal inactivating said memory means, said latter means retaining the memorized armature current Ialm, said first detecting means comprising summation means, means for deriving a signal which is a function of the instantaneous speed of said first motor, capacitive means, relay means, said summation means having dual inputs, said capacitive means coupling said derived signal means to one of said dual inputs, the other of the dual inputs being connected to receive a signal whichis a function of the armature current of said first motor, the summation means, having no output under no load conditions,

said relay means having contacts coupled to said memory means and to said first transport delay means, said relay means being connected to the output of said summation means, whereby when the material enters said first stand rollers, said first motor armature current increases, the summation means delivering said first load detecting signal to the relay means to thereby actuate said memory means and said first transport delay means, second detecting means for sensing the presence of said material in the succeeding second stand rollers, and for developing a second load detecting signal, algebraic summation means actuated in response to said second load detecting signal and adapted to receive the polarized instantaneous armature current lal, of said first motor, and the polarized memorized armature current lalm, and to deliver an algebraic summation signal which becomes zero when lal =Ia1m, speed changing means actuated upon receipt of said second load detecting signal for increasing or decreasing the speed of the second stand motor, said second motor speed changing means being connected to receive said algebraic summation signal, and to change the speed of said second stand motor as a function of said algebraic summation signal, and second transport delay means actuated in response to said second load detecting signal, arranged to receive a secon voltage proportional to the speed of said second motor and to deliver a second transport delay signal which is an inverse function of the second motor speed, said second transport delay signal electrically isolating the first stand from the second stand, the material having now traversed from the first stand to the second stand under substantially no tensile or compressive stress.

3. An interstand tension-compression control system according to claim 2 wherein said deriving means comprises a tachometer generator connected to the shaft of said first stand motor.

4. An interstand tension-compression control system according to claim 2 wherein said memory means comprises in series, a first summation amplifier, circuit interrupting means, and an operational amplifier connected as an integrator, said circuit interrupting means coupling said first summation amplifier and said operational amplifier, said first summation amplifier being adapted to receive as a first input said polarized instantaneous armature current la of said motor, and as a second input, the polarized feedback signal from the output of said operational amplifier, whereby the first transport delay signal actuates said circuit interrupter means to isolate said first summation amplifier from said operational amplifier, the output of said operational amplifier being 8 held at Ialm. l 5. An interesting tension-compression control system according to claim 2 wherein said first transport delay means comprises in series, circuit interrupting means, an operational amplifier connected as an integrator, a first summation amplifier and relay means, said circuit interrupting means actuated in response to said first load detecting signal connecting said first voltage signal to said operational amplifier, the polarized output of said operational amplifier being connected as one input to said first summation amplifier, the other input of said first summation amplifier being a variable signal of a different polarity, said first summation amplifier delivering said first transport delay signal when said polarized signals are equal in magnitude. 6. An interstand tensioncompression control system according to claim 2 wherein said speed changing means comprises an additional motor, a potentiometer, a common voltage source, saidpotentiometer being across said common voltage source and having a slider displaceable in response to the rotational displacement of said additional motor, the displacement of said slider providing an incremental or decremental voltage to the field of said second motor, said additional motor being actuated only upon receipt of said second load detecting signal, the rotational displacement of said motor being a function of said algebraic summation signal. 

1. An interstand tension-compression control system for use in a continuous mill having a plurality of stands, each stand having an electric motor for actuating rollers for successively rolling material to a predetermined cross sectional area comprising: a. first detecting means for sensing the presence of said material in the first stand rollers and for developing a first load detecting signal; b. memory means actuated in response to said first load detecting signal and connected to receive the armature current Ia1 of the first stand motor, for memorizing the armature current Ia1m; c. first transport delay means actuated in response to said first load detecting signal, and arranged to receive a first voltage proportional to the speed of said first motor, and to deliver a first transport delay signal which is an inverse function of the first motor speed, said first transport delay signal inactivating said memory means, said latter means retaining the memorized armature current Ia1m; d. second detecting means for sensing the presence of said material in the succeeding second stand rollers, and for developing a second load detecting signal; e. algebraic summation means actuated in response to said second load detecting signal and adapted to receive the polarized instantaneous armature current Ia1, of said first motor, and the polarized memorized armature current Ia1m, and to deliver an algebraic summation signal which becomes zero when Ia1 Ia1m; f. speed changing means actuated upon receipt of said second load detecting signal for increasing or decreasing the speed of the second stand motor, said second motor speed changing means being connected to receive said algebraic summation signal, and to change the speed of said second stand motor as a function of said algebraic summation signal; and g. second transport delay means actuated in response to said second load detecting signal, arranged to receive a second voltage proportional to the speed of said second motor and to deliver a second transport delay signal which is an inverse function of the second motor speed, said second transport delay signal electrically isolating the first stand from the second stand, the material having now traversed from the first stand to the second stand under substantially no tensile or compressive stress.
 2. An interstand tension-compression control system for use in a continuous mill having a plurality of stands, each stand having an electric motor for actuating rollers for successively rolling material to a predetermined cross sectional area comprising, first detecting means for sensing the presence of said material in the first stand rollers and for developing a first load detecting signal, memory means actuated in response to said first load detecting signal and connected to receive the armature current Ia1 of the first stand motor, for memorizing the armature current Ia1m, first transport delay means actuated in responce to said first load detecting signal, and arranged to receive a first voltage proportional to the speed of said first motor, and to deliver a first transport delay signal which is an inverse function of the first motor speed, said first transport delay signal inactivating said memory means, said latter means retaining the memorized armature current Ia1m, said first detecting mEans comprising summation means, means for deriving a signal which is a function of the instantaneous speed of said first motor, capacitive means, relay means, said summation means having dual inputs, said capacitive means coupling said derived signal means to one of said dual inputs, the other of the dual inputs being connected to receive a signal which is a function of the armature current of said first motor, the summation means, having no output under no load conditions, said relay means having contacts coupled to said memory means and to said first transport delay means, said relay means being connected to the output of said summation means, whereby when the material enters said first stand rollers, said first motor armature current increases, the summation means delivering said first load detecting signal to the relay means to thereby actuate said memory means and said first transport delay means, second detecting means for sensing the presence of said material in the succeeding second stand rollers, and for developing a second load detecting signal, algebraic summation means actuated in response to said second load detecting signal and adapted to receive the polarized instantaneous armature current Ia1, of said first motor, and the polarized memorized armature current Ia1m, and to deliver an algebraic summation signal which becomes zero when Ia1 Ia1m, speed changing means actuated upon receipt of said second load detecting signal for increasing or decreasing the speed of the second stand motor, said second motor speed changing means being connected to receive said algebraic summation signal, and to change the speed of said second stand motor as a function of said algebraic summation signal, and second transport delay means actuated in response to said second load detecting signal, arranged to receive a secon voltage proportional to the speed of said second motor and to deliver a second transport delay signal which is an inverse function of the second motor speed, said second transport delay signal electrically isolating the first stand from the second stand, the material having now traversed from the first stand to the second stand under substantially no tensile or compressive stress.
 3. An interstand tension-compression control system according to claim 2 wherein said deriving means comprises a tachometer generator connected to the shaft of said first stand motor.
 4. An interstand tension-compression control system according to claim 2 wherein said memory means comprises in series, a first summation amplifier, circuit interrupting means, and an operational amplifier connected as an integrator, said circuit interrupting means coupling said first summation amplifier and said operational amplifier, said first summation amplifier being adapted to receive as a first input said polarized instantaneous armature current Ia of said motor, and as a second input, the polarized feedback signal from the output of said operational amplifier, whereby the first transport delay signal actuates said circuit interrupter means to isolate said first summation amplifier from said operational amplifier, the output of said operational amplifier being held at Ia1m.
 5. An interesting tension-compression control system according to claim 2 wherein said first transport delay means comprises in series, circuit interrupting means, an operational amplifier connected as an integrator, a first summation amplifier and relay means, said circuit interrupting means actuated in response to said first load detecting signal connecting said first voltage signal to said operational amplifier, the polarized output of said operational amplifier being connected as one input to said first summation amplifier, the other input of said first summation amplifier being a variable signal of a different polarity, said first summation amplifier delivering said first transport delay signal when said polarized signals are equal in magnitude.
 6. An interstand tension-compression control syStem according to claim 2 wherein said speed changing means comprises an additional motor, a potentiometer, a common voltage source, said potentiometer being across said common voltage source and having a slider displaceable in response to the rotational displacement of said additional motor, the displacement of said slider providing an incremental or decremental voltage to the field of said second motor, said additional motor being actuated only upon receipt of said second load detecting signal, the rotational displacement of said motor being a function of said algebraic summation signal. 